The present invention is generally related to sensing methods and systems. The present invention is additionally related to sensors utilized in automotive and mechanical applications. The present invention is also related to magnetoresistors and Wheatstone bridge circuit configurations. The present invention is additionally related to linear position sensing methods and systems thereof.
Various sensors are known in the magnetic-effect sensing arts. Examples of common magnetic-effect sensors include Hall effect and magnetoresistive technologies. Such magnetic sensors can generally respond to a change in the magnetic field as influenced by the presence or absence of a ferromagnetic target object of a designed shape passing by the sensory field of the magnetic-effect sensor. The sensor can then provide an electrical output, which can be further modified as necessary by subsequent electronics to yield sensing and control information. The subsequent electronics may be located either onboard or outboard of the sensor package.
Many automotive electronic systems utilize position sensors for a number of related applications. When position sensors for automotive electronic systems were originally conceived and developed, such sensors were primarily utilized for the determination of clutch pedal and shift lever positions in automobile transmission applications. Reasonably accurate linear position sensing is required to identify the positions of the clutch pedal and the shift lever, using electrical signals from a non-contacting sensor approach. For example, in automated manual transmission applications, two sensors may be required to sense the shift lever position as it moves in an H-pattern from Reverse to Low to Second to Third gear. For a standard automatic transmission application, where the shift lever moves along a single axis direction, one position sensor may be required to sense whether the shift lever is in one of the Drive-Mode operating positions (i.e., Forward, Reverse, Neutral, Over-Drive, Low, etc.) as well as any positions between such operating conditions.
Many of the sensors utilized in automotive applications are configured as linear position sensors, which provide feedback to a control unit. Many of these types of sensors and related systems are mechanical in nature and are very sensitive to the wearing of contacts, contact contamination, and so forth. The present inventors have recognized that a continuing need exists for improved linear position sensors. The present invention was generated out of a need to find a low-cost linear position sensor for use in an electrically controlled and assisted power steering system being developed for future automotive vehicles.
In a general automobile environment, a torque can be applied to a steering column, which in turn can cause translational movement of a slider body whose position must be sensed. The slider body is typically part of an assembly that includes a helical coil spring and torsion bar connecting two halves of the steering column, the input shaft and output shaft. The amount of slider body movement is linearly related to the amount of torque applied to the steering column. The present inventors have thus designed an improved linear position sensor that solves the foregoing needs and is adaptable to varying position-sensing systems regardless of magnetic strengths and dimensions. It is believed that such an improved linear position sensing method and system will be particularly useful when utilized with steering column applications and mechanical systems thereof.
The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to the present invention and is not intended to be a full description. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole.
It is, therefore, one aspect of the present invention to provide an improved sensor method and system.
It is another aspect of the present invention to provide for a sensor that can be used in automotive and mechanical applications.
The aforementioned aspects of the invention and other objectives and advantages can now be achieved as described herein.
Methods and systems for sensing linear position utilizing a magnetoresistive bridge circuit are disclosed herein. A permanent magnet can be provided having a gap formed therein. The size and shape of the permanent magnet can be selected to produce a magnetic field strength that can force the magnetoresistive bridge circuit into a saturated mode. The magnetoresistive bridge circuit can be located within the gap of the permanent magnet. The magnetoresistive bridge circuit includes a plurality of magnetoresistors, which do not respond to a change in the magnetic field strength created when the ferrous target moves past a face of the magnet. The magnet can be positioned in proximity to the ferrous target, which is typically associated with a slider that moves along a shaft. The magnetoresistive bridge circuit is generally biased by a magnetic field of the magnet. The magnetic bias field is sufficient to saturate the magnetoresistive bridge circuit and a response of the magnetoresistors thereof. An output signal of the magnetoresistive bridge circuit can then be detected such that the output signal is produced by a change in an angle of the magnetic bias field. The output signal can determine a target position with respect to a torque applied to the shaft.